Is there a way to get DS games to use the full top screen on a 3DS?
Solution 1:
There appears to be two modes for playing DS games on the 3DS. If you hold Select+Start while the DS game is loading, it will display in it's "Native Resolution" on the 3DS screens.
Unfortunately, this is going to make the black bars bigger and not smaller. As far as I can tell, this is the only other display mode that the 3DS supports when playing DS games.
It has to do with the different resolutions/aspect ratios of the DS and the 3DS. Similar things happened when playing GB games on the GBA.